The genus Brachydontium consists of five rare species. Four of them have a narrow distribution with B. curvisetum Crum endemic to Mexico, B. flexisetum (Hampe) Par. restricted to Colombia, B. intermedium I. G. Stone only known from Australia, and B. olsonii Bowers & Allen confined to Honduras. Only B. trichodes (Web.) Milde is found to be more widely distributed in the Northern Hemisphere.